First DivisionCharlton Athletic paid £400,000 for Allen's services in March 1996.[2] He scored six goals in 21 appearances in the league and League Cup in his first full season with the club[6] but chances became harder to come by for Allen, as he made only 14 first-team appearances and could net only two goals during the 1997–98 season as Charlton were promoted to the Premier League.[7] He then made only one appearance for the club in the 1998–99 season,[8] and then joined Division Two side Colchester United in February 1999.[2] This spelt the end of his time with Charlton, having scored nine goals in 40 league appearances.[5]

Recruited by Colchester manager Mick Wadsworth,[2] Allen made his debut for the U's in a 1–1 home draw with Reading on 27 February 1999, before being replaced by Steve Forbes after 68 minutes.[9] He scored one goal while on loan with the club, a 40th minute equaliser during a 2–2 draw with Oldham Athletic on 9 March.[10] Allen made four appearances in total during his short stay at Layer Road.[5]

Allen was placed on the transfer list at Charlton and transferred to Grimsby Town in the summer of 1999, who at the time plied their trade in the First Division under Alan Buckley.[2] He scored nine goals in 36 games in all competitions in the 1999–2000 season[11] but found himself limited to just 25 appearances in the 2000–01 season, being limited by injuries and only managing to score six goals.[12] The 2001–02 season saw a return of 5 goals in 31 games, but his injury record and Grimsby's financial plight saw Allen released at the end of the season.[12] He ended his Grimsby stay with 15 goals in 80 league games.[5]

Ambitious Isthmian League club Hornchurch signed Allen in September 2003 following trials with a number of clubs.[21] He was one of a number of former professional players with Football League experience in a squad that knocked League side Darlington out of the FA Cup in 2003.[22] However, with the club facing financial turmoil, Hornchurch began releasing players during the 2003–04 season, with Allen one of the squad members released.[23]

Following his release from Hornchurch, Allen quickly joined Conference South side Ford United, who would later change name to become Redbridge. Having scored on his debut, his stint did not last long, and was subsequently released in July 2004, with club manager Craig Edwards stating that the club would prefer "to go with younger players" for the coming season and that there were financial implications. Allen then joined Billericay Town on trial, scoring in a pre-season friendly against Grays Athletic.[23]

After retiring from the game in 2004, Allen became a PE teacher and became an academy coach at Tottenham Hotspur, where he is currently running the under-15 side.[2][24] In addition to his coaching, Allen has worked in the media, providing co-commentary for Sky SportsFootball First programme and also for radio coverage.[25]